SOS mode is a mobile device status that restricts the phone to emergency calls only. This mode is typically activated when the device cannot connect to its usual network provider, either due to lack of coverage, a SIM card issue, or network failure. In SOS mode, users are unable to make regular calls, send texts, or use mobile data, but can still contact emergency services like 911 or 112. This feature ensures that users can reach help in critical situations even when normal network access is unavailable, enhancing personal safety and security.